WO2021129828A1 - 特高压直流低端换流器阀区接地故障控制方法及控制装置 - Google Patents

特高压直流低端换流器阀区接地故障控制方法及控制装置 Download PDF

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Publication number
WO2021129828A1
WO2021129828A1 PCT/CN2020/139576 CN2020139576W WO2021129828A1 WO 2021129828 A1 WO2021129828 A1 WO 2021129828A1 CN 2020139576 W CN2020139576 W CN 2020139576W WO 2021129828 A1 WO2021129828 A1 WO 2021129828A1
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Prior art keywords
low
converter
switch
end converter
current
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PCT/CN2020/139576
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English (en)
French (fr)
Inventor
卢东斌
赵森林
李海英
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南京南瑞继保电气有限公司
南京南瑞继保工程技术有限公司
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Application filed by 南京南瑞继保电气有限公司, 南京南瑞继保工程技术有限公司 filed Critical 南京南瑞继保电气有限公司
Priority to BR112022010341-7A priority Critical patent/BR112022010341B1/pt
Publication of WO2021129828A1 publication Critical patent/WO2021129828A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • This application relates to the technical field of high-voltage direct current power transmission, and in particular to a method and a control device for controlling a ground fault in the valve area of a UHV DC low-end converter.
  • UHV DC transmission systems generally use two converters in series to form a DC pole. According to existing projects, they are divided into conventional UHV DC transmission systems, hierarchical access UHV DC transmission systems and hybrid UHV DC transmission systems.
  • the conventional UHV DC transmission system is a DC pole high-end and low-end converters, both of which are grid-commutated converters, and they are connected to the same AC grid.
  • Hierarchical access to the UHV DC transmission system is that the high-end and low-end converters of a DC pole are all grid-commutated converters, and they are respectively connected to two different AC power grids.
  • Hybrid UHV DC transmission systems are divided into two types: inter-station hybrid, inter-electrode hybrid and intra-electrode hybrid.
  • the inter-station hybrid hybrid UHV DC transmission system uses voltage source converters.
  • the converter station of a DC pole is high and low.
  • Both the end converters are voltage source converters
  • the hybrid UHV DC transmission system using voltage source converters for hybrid UHV DC transmission systems uses voltage source converters.
  • Both the high and low end converters of the DC pole are voltage source converters, and the poles are mixed.
  • the hybrid UHV DC transmission system adopts the grid-commutated converter and the high-end converter of the DC pole of the voltage source converter.
  • the high-end and low-end converters are respectively the grid-commutated converter and the voltage source converter.
  • the prior art isolates the fault by blocking the entire DC pole. After the fault is isolated, the single-max return line is used to continue operation , Or switch to metal loop operation, or restart the non-faulty converter of the DC pole to achieve bipolar balanced operation.
  • the existing technology mainly has the following problems: after the entire DC pole is blocked, a large current will flow through the ground electrode line, which will easily cause the transformer in the nearby substation to have DC bias and cause the transformer to saturate; after the entire DC pole is blocked, if the power is transmitted Larger, more DC power will be lost; after blocking the entire DC pole, more fault current will flow through the fault point.
  • the embodiment of the present application provides a method for controlling the ground fault of the valve area of the UHV DC low-end converter, which is applied to the low-end converter of the DC pole of the UHV DC transmission system, and the UHV DC transmission system includes double DC poles.
  • the DC pole includes at least two converters connected in series, and the low-end converter is a converter close to the polar neutral bus.
  • the control method includes: controlling the low-end converter to lock; controlling the special feature The DC currents of the double DC poles of the HVDC transmission system are equal; the low-end converter is isolated; the converters other than the low-end converter continue to operate.
  • the low-end converter includes at least one of a grid commutated converter or a voltage source converter.
  • the dual DC pole operation includes: each of the DC poles has at least one converter in operation; the full valve group operation includes: the DC pole where the low-end converter is located is divided by the low At least one converter is in operation besides the end converter.
  • the occurrence of a ground fault in the valve area of the low-end converter includes: a ground fault occurs in the low-end converter, and a ground fault occurs in the connection line between the low-end converter and the converter transformer At least one of the occurrence of a ground fault in the winding on the valve side of the converter transformer.
  • the detecting that a ground fault occurs in the valve area of the low-end converter includes: detecting that the absolute value of the difference between the high-voltage bus current and the low-voltage bus current on the DC side of the low-end converter is greater than The set current difference.
  • the controlling the low-end converter to lockout includes: controlling the low-end converter to stop the trigger pulse and close the The second bypass switch of the low-end valve group where the low-end converter is located, trips the converter transformer inlet switch of the low-end converter, and the second bypass switch is connected to the low-end converter Positive and negative.
  • the controlling the low-end converter to lockout includes: when the low-end converter is in rectification operation, selecting the rectifier-side converter The first blocking mode of the inverter or the second blocking mode of the rectifier-side converter controls the low-side converter to lock; when the low-side converter is in inverter operation, select the inverter-side converter first A blocking mode or the second blocking mode of the inverter-side converter controls the low-end converter to be blocked.
  • the first locking method of the rectifier-side converter includes: controlling the low-end converter in rectification operation to stop the trigger pulse, and the corresponding inverter operation in the inverter controls the trigger angle to be 90 degrees. ; Control to trip the converter transformer inlet switch of the low-end converter, close the second bypass switch of the low-end converter, and put the inverter in the corresponding inverter operation into the bypass pair and close The second bypass switch is connected to the anode and the cathode of the low-side converter.
  • the second locking method of the rectifier-side converter includes: controlling the low-side converter to put into the bypass pair, closing the second bypass switch, and simultaneously tripping the low-side converter Incoming line switch of the converter transformer, the corresponding inverter control trigger angle of inverter operation is 90 degrees, the second bypass switch is connected to the anode and cathode of the low-side converter; and the corresponding inverter is controlled. The inverter in operation is put into the bypass pair and the bypass switch is closed.
  • the first blocking method of the inverter-side converter includes: controlling the inverter transformer inlet switch of the low-end converter operating in the inverter to be tripped, turning on the bypass pair, and closing the second Bypass switch, the corresponding rectifying operation converter has a control trigger angle of 90 degrees, and the second bypass switch is connected to the anode and cathode of the low-end converter; controls the corresponding rectifying operation converter Turn on the bypass pair and turn on the bypass switch.
  • the second blocking method of the inverter-side converter includes: controlling the low-side converter in inverter operation to put into a bypass pair, closing the second bypass switch, and simultaneously tripping the low-side converter.
  • the input switch of the converter transformer of the low-end converter, the corresponding rectifying operation converter has a control trigger angle of 90 degrees, and the second bypass switch is connected to the anode and cathode of the low-end converter; The corresponding rectified converter is put into the bypass pair, and the bypass switch is closed.
  • the controlling the DC currents of the dual DC poles of the UHV DC transmission system to be equal includes: given the same DC current reference value for the converters of the dual DC poles;
  • the high-voltage bus current or the low-voltage bus current or the pole bus current of other converters is the DC current reference value;
  • the DC current reference value is based on the active power, reactive power, fault current limit or current limit of the UHV DC transmission system
  • the ground current limit requirement is determined; if the low-side converter that fails is rectified, the converters on the rectifier side except the low-side converter adopt current control to control the rectifier side to remove the low-side converter.
  • the DC currents of the converters other than the low-end converter are equal, and the inverter on the inverter side is operated under the maximum firing angle control or DC voltage control; if the low-end converter that fails is in inverter operation, the inverter The converters other than the low-end converter on the other side send fault information to the rectifier side, and the rectifier side controls the DC currents of the converters of the double DC poles to be equal, or adopts current control to control the inverter side except the low-end converter.
  • the DC currents of the converters other than the end converters are equal, and the converters on the rectifier side operate under DC voltage control.
  • the isolating the low-end converter includes: closing the first bypass switch of the low-end valve group where the low-end converter is located, and separating the low-end valve where the low-end converter is located Group of the second bypass switch, valve group switch and bus switch, the first bypass switch is connected in parallel with the low-end converter, and the second bypass switch is connected to the two low-end converters.
  • the valve group switch connects the low-end converter and the valve group connection line
  • the busbar switch connects the low-end converter and the extremely neutral bus.
  • the isolating the low-end converter includes: if the high-voltage bus current on the DC side of the low-end converter is greater than the low-voltage bus current, separating the valve group switch, controlling the double DC pole DC current to zero, and then separating The second bypass switch restores the dual DC-pole DC current, and then separates the bus switch; if the high-voltage bus current on the DC side of the low-side converter is less than the low-voltage bus current, separate the bus switch to control the dual DC If the pole DC current is zero, the second bypass switch is separated to restore the dual DC pole DC current, and then the valve group switch is opened.
  • the separation of the second bypass switch, valve group switch and bus switch of the low-side converter includes: if the low-side converter If the high-voltage bus current on the DC side of the low-end converter is greater than the low-voltage bus current, the valve group switch is separated first, then the second bypass switch is separated, and then the bus switch is separated; if the high-voltage bus on the DC side of the low-end converter If the current is less than the low-voltage bus current, the bus switch is first separated, then the second bypass switch is separated, and then the valve group switch is separated.
  • the separation of the second bypass switch, valve group switch and bus switch of the low-end converter includes: if the low-end converter is DC If the high-voltage bus current on the DC side of the low-side converter is greater than the low-voltage bus current, first separate the second bypass switch, then separate the valve group switch, and then separate the bus switch; if the high-voltage bus current on the DC side of the low-side converter is less than For low-voltage bus current, the bus switch is first separated, then the valve group switch is separated, and then the second bypass switch is separated.
  • breaking current value of any one of the second bypass switch, valve group switch, and bus switch is greater than the high-voltage bus current or the low-voltage bus current on the DC side of the low-side converter, And the breaking current of the busbar switch is the largest.
  • the second bypass switch, valve group switch and busbar switch that separate the low-end converter include: if the DC side of the low-end converter If the high-voltage bus current of the low-side converter is greater than the low-voltage bus current, first separate the valve block switch, then separate the bus switch, and then separate the second bypass switch; if the high-voltage bus current on the DC side of the low-side converter is less than the low-voltage For the bus current, first separate the second bypass switch, then separate the bus switch, and then separate the valve group switch.
  • the continuous operation of the converters other than the low-end converter includes: the converters other than the low-end converter continue to operate at the station where the low-end converter is located In operation, other stations exit the converter corresponding to the low-end converter, and the remaining converters continue to operate.
  • the method before the isolation of the low-end converter, the method further includes: increasing the range of the range protection differential current setting of the DC pole where the low-end converter is located or increasing the low-end converter The range protection of the DC pole where the converter is located delays the fixed value or the shield range protection, until the low-end converter is isolated.
  • the method further includes: pulling on the metal return line transfer switch or the neutral bus grounding switch to disconnect the connection between the converter station and the earth.
  • the return line changeover switch connects the bipolar neutral bus and the grounding pole line
  • the neutral bus grounding switch connects the bipolar neutral bus and the grounding grid in the station.
  • the control method further includes: after isolating the low-side converter, closing the metal loop transfer switch or the Neutral bus grounding switch.
  • the embodiment of the present application also provides a ground fault control device for the valve area of the UHV DC low-end converter, which applies the above-mentioned method for controlling the ground fault of the valve area of the UHV DC low-end converter.
  • the control device includes a detection unit and The control unit, the detection unit detects the high-voltage bus current and the low-voltage bus current of the low-end converter, detects the extremely neutral bus current, and detects the pole where the low-end converter is located except for the low-end converter The high-voltage bus current, low-voltage bus current or pole bus current of other converters are detected, and the pole bus voltage and the pole neutral bus voltage are detected; the control unit determines that the UHV DC transmission system is operating in dual DC poles, and the low When the full valve group of the DC pole where the low-end converter is located and a ground fault is detected in the valve area of the low-end converter, the low-end converter is controlled to lock, and at the same time, the two DC poles are controlled to have equal DC
  • Fig. 1 is a schematic diagram of a main circuit of an UHV DC transmission system provided by an embodiment of the present application.
  • Fig. 2 is a schematic flowchart of a method for controlling a ground fault in a valve zone of an UHV DC low-end converter provided by an embodiment of the present application.
  • Figure 3 is a schematic diagram of the valve area grounding fault location of the low-end converter on the rectifier side.
  • Fig. 4A is a graph of simulation test results when an F1 ground fault occurs in a low-end converter on the rectifier side of the prior art.
  • FIG. 4B is a diagram of simulation test results when an F1 ground fault occurs in the low-end converter on the rectifier side provided by the embodiment of the present application.
  • Fig. 5A is a graph of simulation test results when an F2 ground fault occurs in a low-end converter on the rectifier side of the prior art.
  • FIG. 5B is a diagram of simulation test results when an F2 ground fault occurs in the low-end converter on the rectifier side provided by the embodiment of the present application.
  • Fig. 6 is a schematic structural diagram of a ground fault control device for a valve area of an UHV DC low-end converter provided by an embodiment of the present application.
  • Fig. 1 is a schematic diagram of a main circuit of an UHV DC transmission system provided by an embodiment of the present application.
  • the main circuit of UHV DC transmission system includes rectifier station 100, inverter station 200, first DC line 150, second DC line 160, rectifier station ground electrode line 114, rectifier station ground electrode 115 and inverter station ground electrode line 214 , Inverter station grounding pole 215.
  • the rectifier station 100 includes a first DC pole I110, a second DC pole II120, a first AC filter bank 118, a first AC system 140, a converter transformer inlet switch and a metal loop transfer switch 113.
  • the first DC pole I110 includes a first high-end valve group 111, a first low-end valve group 112, a first high-end converter transformer 116, a first low-end converter transformer 117, a first DC filter 93, and a first flat. Wave reactor 91.
  • the first high-end valve group 111 and the first low-end valve group 112 are connected in series.
  • the first high-end valve group 111 includes a first high-end converter 1, a first high-end valve group, a first bypass switch 11, a first high-end valve group and a second bypass switch 12, a first high-end valve group bus switch 13, a first High-end valve group valve group switch 14.
  • the first bypass switch 11 of the first high-end valve group is connected in parallel with the first high-end converter 1.
  • the first high-end valve group and the second bypass switch 12 are connected to both ends of the first high-end inverter 1.
  • the first high-end valve group valve group switch 14 connects the first high-end inverter 1 and the valve group connection line.
  • the first high-end valve group bus switch 13 connects the first high-end inverter 1 and the pole bus.
  • the first low-end valve group 112 includes a first low-end converter 2, a first low-end valve group, a first bypass switch 21, a first low-end valve group and a second bypass switch 22, and a first low-end valve group valve Group switch 23, first low-end valve group bus switch 24.
  • the first bypass switch 21 of the first low-end valve group is connected in parallel with the first low-end converter 2
  • the second bypass switch 22 of the first low-end valve group is connected to both ends of the third low-end converter 6.
  • a low-end valve group valve group switch 23 connects the first low-end converter 2 and the valve group connection line
  • the first low-end valve group bus switch 24 connects the first low-end converter 2 and the extremely neutral bus.
  • the first high-end converter 1 and the first low-end converter 2 include at least one of a grid commutated converter or a voltage source converter.
  • the power grid commutation converter includes but is not limited to at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit.
  • the pulsating bridge circuit includes, but is not limited to, a semi-controlled power semiconductor device that cannot be turned off, generally a thyristor device.
  • Voltage source converters include, but are not limited to, two-level converters, diode-clamped multi-level converters, modular multi-level converters MMC, hybrid multi-level converters HMC, two-level converters At least one of a combined converter CSL and a stacked two-level converter CTL.
  • the converter includes, but is not limited to, a fully controllable power semiconductor device that can be turned off.
  • the above-mentioned modular multilevel converter MMC includes, but is not limited to, a modular multilevel converter MMC with a half-bridge sub-module structure, a modular multi-level converter MMC with a full-bridge sub-module structure, a half-bridge and a full-bridge sub-module structure. At least one type of modular multilevel converter MMC with a bridge hybrid sub-module structure.
  • the second DC pole II120 includes a second low-end valve group 121, a second high-end valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second DC filter 94, and a second smoothing reactor ⁇ 92.
  • the second low-end valve group 121 and the second high-end valve group 122 are connected in series.
  • the second high-end valve group 122 includes a second high-end inverter 4, a second high-end valve group first bypass switch 41, a second high-end valve group second bypass switch 42, a second high-end valve group valve group switch 43, Two high-end valve group bus switch 44.
  • the first bypass switch 41 of the second high-end valve group is connected in parallel with the second high-end converter 4, and the second bypass switch 42 of the second high-end valve group is connected to both ends of the second high-end converter 4.
  • the second high-end valve group The valve group switch 43 connects the second high-end converter 4 and the valve group connection line, and the second high-end valve group bus switch 44 connects the second high-end converter 4 and the pole bus.
  • the second low-end valve group 121 includes a second low-end converter 3, a second low-end valve group first bypass switch 31, a second low-end valve group second bypass switch 32, and a second low-end valve group bus Switch 33, the second low-end valve group valve group switch 34.
  • the first bypass switch 31 of the second low-end valve group is connected in parallel with the second low-end converter 3
  • the second bypass switch 32 of the second low-end valve group is connected to both ends of the second low-end converter 3.
  • the second low-end valve group valve group switch 34 connects the second low-end converter 3 and the valve group connection line
  • the second low-end valve group bus switch 33 connects the second low-end converter 3 and the extremely neutral bus.
  • the second high-end converter 4 and the second low-end converter 3 include at least one of a grid commutated converter or a voltage source converter.
  • the inverter station 200 includes a third DC pole I210, a fourth DC pole II220, a second AC filter bank 218, a second AC system 240, and a converter transformer inlet switch.
  • the third DC pole I210 includes a third high-end valve group 211, a third low-end valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third DC filter 97, and a third smoothing reactor. ⁇ 95.
  • the third high-end valve group 211 and the third low-end valve group 212 are connected in series.
  • the third high-end valve group 211 includes the third high-end converter 5, the third high-end valve group first bypass switch 51, the third high-end valve group second bypass switch 52, the third high-end valve group bus switch 53, and the third High-end valve group valve group switch 54.
  • the first bypass switch 51 of the third high-end valve group is connected in parallel with the third high-end converter 5, and the second bypass switch 52 of the third high-end valve group is connected to both ends of the third high-end converter 5.
  • the third high-end valve group The valve group switch 54 connects the third high-end converter 5 and the valve group connection line, and the third high-end valve group bus switch 53 connects the third high-end converter 5 and the pole bus.
  • the third low-end valve group 212 includes a third low-end converter 6, a third low-end valve group first bypass switch 61, a third low-end valve group second bypass switch 62, and a third low-end valve group valve Group switch 63, the third low-end valve group bus switch 64.
  • the first bypass switch 61 of the third low-end valve group is connected in parallel with the third low-end converter 6, and the second bypass switch 62 of the third low-end valve group is connected to both ends of the third low-end converter 6.
  • the three-low-end valve group valve group switch 63 connects the third low-end converter 6 and the valve group connection line, and the third low-end valve group bus switch 64 connects the third low-end converter 6 and the extremely neutral bus.
  • the third high-end converter 5 and the third low-end converter 6 include at least one of a grid commutated converter or a voltage source converter.
  • the fourth DC pole II220 includes a fourth low-end valve group 221, a fourth high-end valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a second DC filter 98, and a second smoothing reactor ⁇ 96.
  • the fourth low-end valve group 221 and the fourth high-end valve group 222 are connected in series.
  • the fourth high-end valve group 222 includes a fourth high-end converter 8, a fourth high-end valve group first bypass switch 81, a fourth high-end valve group second bypass switch 82, a fourth high-end valve group valve group switch 83, and a fourth high-end valve group second bypass switch 82.
  • the first bypass switch 81 of the fourth high-end valve group is connected in parallel with the fourth high-end converter 8, and the second bypass switch 82 of the fourth high-end valve group is connected to both ends of the fourth high-end converter 8.
  • the valve group switch 83 connects the fourth high-end converter 8 and the valve group connection line
  • the fourth high-end valve group bus switch 84 connects the fourth high-end converter 8 and the pole bus.
  • the fourth low-end valve group 221 includes a fourth low-end converter 7, a fourth low-end valve group first bypass switch 71, a fourth low-end valve group second bypass switch 72, and a fourth low-end valve group bus Switch 73, the fourth low-end valve group valve group switch 74.
  • the first bypass switch 71 of the fourth low-end valve group is connected in parallel with the fourth low-end converter 7, and the second bypass switch 72 of the fourth low-end valve group is connected to both ends of the fourth low-end converter 7.
  • the four-low-end valve group valve group switch 74 connects the fourth high-end converter 7 and the valve group connection line, and the fourth low-end valve group bus switch 73 connects the fourth low-end converter 7 and the extremely neutral bus.
  • the fourth high-end converter 8 and the fourth low-end converter 7 include at least one of a grid commutated converter or a voltage source converter.
  • the various switches mentioned above include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valve groups.
  • both the high-end converter and the low-end converter of the DC poles of the rectifier station 100 and the inverter station 200 are grid-converted converters, and the high-end converter and the low-end converter are connected to the same AC grid, then Conventional UHV DC transmission system.
  • both the high-end converter and the low-end converter of the DC poles of the rectifier station 100 and the inverter station 200 are grid-commutated converters, and the high-end converter and the low-end converter are connected to different AC power grids, they are divided Layer access to UHV DC transmission system.
  • the first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter of the first DC pole I110 and the second DC pole II120 of the rectifier station 100 3 are power grid commutated converters
  • the third high-end converter of the third DC pole I210 and the fourth DC pole II220 of the inverter station 200 5 are both voltage source converters, which are hybrid UHV DC transmission systems mixed between stations.
  • first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter of the first DC pole I110 and the second DC pole II120 of the rectifier station 100 3 are power grid commutated converters.
  • the third high-end converter 5 and the fourth high-end converter 8 of the third DC pole I210 and the fourth DC pole II220 of the inverter station 200 are grid commutated converters.
  • the third low-end converter 6 and the fourth low-end converter 7 are voltage source converters, which are hybrid UHV DC transmission systems that are mixed within the poles.
  • the rectifier station 100 is connected to the ground electrode 115 through the ground electrode line 114.
  • the inverter station 200 is connected to the ground electrode 215 through the ground electrode line 214.
  • the first AC system 140 of the rectifier station 100 connects the first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter 3 through its first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter 3.
  • the alternating current is converted into direct current, and is transmitted to the inverter station 200 through the DC lines 150 and 160.
  • the inverter station 200 passes its third high-end converter 5, third low-end converter 6, fourth high-end converter 8 and second
  • the four-low-end converter 7 converts the DC power into AC power and sends it to the second AC system 240 of the inverter station 200, thereby realizing the forward transmission of DC power.
  • the converter of the rectifier station generally runs under current control, and the converter of the inverter station generally runs under voltage control or maximum firing angle control (AMAX). It should be pointed out that the maximum firing angle control (AMAX) is only applicable to grid-commutated converters, not to voltage source converters.
  • the analog signals collected by the rectifier station 100 and the inverter station 200 are: the high-voltage bus current IDC1P and the low-voltage bus current IDC1N on the DC side of the high-end converter, the high-voltage bus current IDC2P and the low-voltage bus current IDC2N on the DC side of the low-end converter, Polar neutral bus current IDNC, polar bus current IDL, ground electrode circuit current IDEL, polar bus voltage UDL and polar neutral bus voltage UDN.
  • Fig. 2 is a schematic flowchart of a method for controlling a ground fault in a valve zone of an UHV DC low-end converter provided by an embodiment of the present application.
  • the UHV DC transmission system includes dual DC poles, the DC poles include at least two converters connected in series, and the low-end converter is a converter close to the polar neutral bus.
  • the DC poles include at least two converters connected in series
  • the low-end converter is a converter close to the polar neutral bus.
  • Each DC pole has at least one converter in operation.
  • Full valve group operation At least two converters are operating at the DC pole.
  • a ground fault occurs in the valve area of the low-end converter: it includes at least a ground fault in the low-end converter, a ground fault in the connecting line between the low-end converter and the converter transformer, and a ground fault in the valve-side winding of the converter transformer.
  • a ground fault in the low-end converter includes at least a ground fault in the low-end converter, a ground fault in the connecting line between the low-end converter and the converter transformer, and a ground fault in the valve-side winding of the converter transformer.
  • a ground fault is detected in the valve area of the low-end converter: It is detected that the absolute value of the difference between the high-voltage bus current and the low-voltage bus current on the DC side of the low-end converter is greater than the set current difference.
  • a ground fault in the valve area of the low-end converter is judged by the converter differential protection action.
  • the criterion formula for the converter differential protection action is as follows.
  • IDiff_v
  • IRes_v
  • IDC2P is the high-voltage bus current on the DC side of the low-end converter
  • IDC2N is the low-voltage bus current on the DC side of the low-end converter
  • Iv_set is the starting current fixed value
  • kv_set is the ratio coefficient
  • the full valve group is operating, that is, the high-end converter and the low-end converter of the DC pole operate at the same time and the other DC pole has at least one converter.
  • the control method is as follows.
  • the low-end converter is controlled to lock.
  • the low-end converter is a voltage source converter
  • the first low-end converter 2 is a voltage source converter
  • the first low-end converter 2 is controlled to be blocked to immediately stop the trigger pulse, and the first low-end converter is closed
  • the second bypass switch 22 of the valve group trips the first low-side converter transformer inlet switch 132 of the first low-side converter 2, and the second bypass switch 22 of the first low-side valve group is connected to the first low-side converter The positive and negative poles of the flow device 2.
  • the low-end converter is a grid-commutated converter
  • control the low-end converter to lock according to the rectification or inverter operation state to choose different blocking methods
  • select the following two kinds of locks Either way: the first locking method of the rectifier side converter and the second locking method of the rectifier side converter.
  • the rectifier station 100 if the first low-end converter 2 of the first DC pole I110 is rectified and operated, if the first blocking method of the rectifier side converter is adopted: the first DC pole I110 of the rectifier station 100 A low-end converter 2 immediately stops sending trigger pulses, and the third low-end converter 6 of the third DC pole I210 of the inverter station 200 controls the trigger angle to be 90 degrees; the first DC pole I110 of the rectifier station 100 The low-end converter 2 trips the first low-end converter transformer inlet switch 132, closes the first low-end valve group and the second bypass switch 22, and the third low-end commutation of the third DC pole I210 of the inverter station 200 The device 6 is put into the bypass pair, and the second bypass switch 62 of the third low-end valve group is closed.
  • the rectifier station 100 if the first low-side converter 2 of the first DC pole I110 is rectified and operated, if the second blocking method of the rectifier side converter is adopted: the first DC pole I110 of the rectifier station 100 A low-end converter 2 is put into the bypass pair, the first low-end valve group and the second bypass switch 22 are closed, and the first low-end converter transformer inlet switch 132 is opened at the same time, and the third DC pole I210 of the inverter station 200 The third low-end converter 6 controls the firing angle of 90 degrees; the third low-end converter 6 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, and the second bypass of the third low-end valve group is closed ⁇ 62 ⁇ Switch 62.
  • the inverter station 200 Taking the inverter station 200 as an example, if the third low-side converter 6 of the third DC pole I210 is in inverter operation, if the inverter side converter is used the first locking method: the third DC pole I210 of the inverter station 200 The third low-end converter 6 trips off the third low-end converter transformer inlet switch 232, and the third low-end converter transformer inlet switch 232 is tripped and then puts into the bypass pair, closing the third low-end valve group No.
  • the third low-side converter 6 of the third DC pole I210 is in inverter operation
  • the second blocking method of the inverter side converter is adopted: the third DC pole I210 of the inverter station is the third The low-end converter 6 is put into the bypass pair, the second bypass switch 62 of the third low-end valve group is closed, and the third low-end converter transformer inlet switch 232 is opened at the same time, and the first DC pole I110 of the rectifier station 100
  • the first low-end converter 2 controls the trigger angle to be 90 degrees; the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 is put into the bypass pair, and the second bypass switch of the first low-end valve group is closed twenty two.
  • the DC current of the double DC poles or the DC current of the converter is the high voltage bus current, the low voltage bus current or the pole bus current of the DC side of the converter except the faulty low-end converter.
  • the DC current reference value is determined according to the active power, reactive power, fault current limit or ground current limit requirements of the UHV DC transmission system.
  • the third high-end converter 5 or the third low-end converter 6 of the third DC pole I210 of the inverter station 200 controls the DC voltage or controls the maximum firing angle.
  • the fault information is transmitted to the rectifier station 100 to control the first high-end converter of the first DC pole I110 of the rectifier station 100 1 or the DC current of the first low-end converter 2 is equal to the DC current of the converter of the second DC pole II120, and the third high-end converter 5 of the third DC pole I210 of the inverter station 200 controls the DC voltage or controls Maximum firing angle.
  • the first low-end converter 2 isolates the first low-end converter 2, close the first bypass switch 21 of the first low-end valve group, and separate the second bypass switch 22 of the first low-end valve group. And the first low-end valve group valve group switch 23, the first low-end valve group bus switch 24.
  • the first bypass switch 21 of the first low-end valve group is connected in parallel with the first low-end converter 2, and the second bypass switch 22 of the first low-end valve group is connected to both ends of the first low-end converter 2.
  • a low-end valve group valve group switch 23 connects the first low-end converter 2 and the valve group connection line, and the first low-end valve group bus switch 24 connects the first low-end converter 2 and the extremely neutral bus.
  • the breaking currents of the first low-end valve group, the second bypass switch 22, the first low-end valve group switch 23, and the first low-end valve group bus switch 24 are all smaller than the DC side of the first low-end converter 2 If the high-voltage bus current IDC2P or the low-voltage bus current IDC2N is the larger value, then the low-end converter 2 is isolated according to the following two conditions.
  • the first low-end valve group valve group switch 23 to control the DC current of the double DC poles to zero, and then separate The second bypass switch 22 of the first low-end valve group restores the double direct current to the normal value, and then the bus switch 24 of the first low-end valve group is opened.
  • the first low-end valve group bus switch 24 to control the dual DC pole DC current to zero, and then separate the first The second bypass switch 22 of the low-end valve group restores the double direct current, and then the first low-end valve group valve group switch 23 is opened.
  • the breaking current of any one of the first low-end valve group, the second bypass switch 22, the first low-end valve group valve group switch 23, and the first low-end valve group bus switch 24 is greater than the low-end converter 2 DC
  • the low-end converter 2 DC For the larger value of the high-voltage bus current IDC2P or low-voltage bus current IDC2N on the side, isolate the low-end converter according to the following conditions.
  • breaking current of the second bypass switch 22 of the first low-end valve group is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 is greater than the low-voltage bus current IDC2N, first separate the first low-end valve group
  • the valve group switch 23 is separated from the first low-end valve group and the second bypass switch 22, and then the first low-end valve group bus switch 24 is separated.
  • breaking current of the second bypass switch 22 of the first low-end valve group is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 is less than the low-voltage bus current IDC2N, first separate the first low-end valve group
  • the bus switch 24 separates the first low-end valve group and the second bypass switch 22, and then separates the first low-end valve group valve group switch 23.
  • breaking current of the first low-side valve group and the first valve group valve group switch 23 is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-side converter 2 is greater than the low-voltage bus current IDC2N, first separate the first low-side
  • the second bypass switch 22 of the valve group is separated from the first low-end valve group valve group switch 23, and then the first low-end valve group bus switch 24 is separated.
  • breaking current of the first low-end valve group and the first valve group valve group switch 23 is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 is less than the low-voltage bus current IDC2N, first separate the first low-side The valve group bus switch 24 is separated from the first low-end valve group valve group switch 23, and then the first low-end valve group second bypass switch 22 is separated.
  • breaking current of the first busbar switch 24 of the first low-end valve group is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 is greater than the low-voltage bus current IDC2N, first separate the first low-end valve group valve
  • the group switch 23 is separated from the first low-end valve group bus switch 24, and then the first low-end valve group second bypass switch 22 is separated.
  • breaking current of the first bus switch 24 of the first low-end valve group is the largest, and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 is less than the low-voltage bus current IDC2N, first separate the first low-end valve group.
  • the two bypass switches 22 are separated from the first low-end valve group bus switch 24, and then the first low-end valve group valve group switch 23 is separated.
  • the remaining converters continue to operate as the first high-end converter 1 of the first DC pole I110 of the rectifier station 100, and the second high-end converter 4 and the second low-end converter 3 of the second DC pole II120 continue.
  • the inverter station 200 exits the third low-end converter 6 of the third DC pole I210, the third high-end converter 5 of the third DC pole I210, the fourth high-end converter 8 of the fourth DC pole II220 and The fourth low-end converter 7 continues to operate.
  • the low-end converter detects a ground fault in the valve area of the low-end converter, increase the range protection differential current setting of the DC pole where the low-end converter is located Or increase the range protection delay setting of the DC pole where the low-end converter is located or the shielded range protection, the differential protection of the shielded valve group connection line, and then open the range protection and valve group after the low-end converter is isolated. Connection line differential protection.
  • the differential current of the range protection is the difference between the sum of the polar neutral bus current, the DC filter current, the polar neutral bus impulse capacitor current and the polar neutral bus arrester current and the polar bus current.
  • the differential current of the valve group connection line is the difference between the low-voltage bus current on the DC side of the high-end converter and the high-voltage bus current on the DC side of the low-end converter.
  • the DC pole where the low-end converter is located is operated in full valve group and the valve area ground fault of the low-end converter is detected, the whole is not blocked
  • the DC pole is only a low-end converter that blocks the fault.
  • bipolar balance control the current of the normal operating pole is introduced to the pole bus of the faulty pole, so as to prevent the current of the normal operating pole from flowing into the fault point too much.
  • more converters are ensured to operate to avoid the loss of large DC transmission power.
  • Figure 3 shows the location of a ground fault in the valve area of the low-end converter on the rectifier side.
  • F1 is a ground fault of the low-end converter.
  • F2 is a ground fault on the connection line between the low-end converter and the converter transformer.
  • Fig. 4A is a graph of simulation test results when an F1 ground fault occurs in a low-end converter on the rectifier side of the prior art.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral line current
  • IDEL is the ground pole line current
  • POWER is the pole power
  • X_BLOCK_MC1 is the pole lock signal
  • BLK_RUN_U_PROT is the inverter lock.
  • BLOCK_IND_V1 is the high-end converter blocking signal
  • BLOCK_IND_V2 is the low-end converter blocking signal.
  • the UHV DC transmission system has a rated voltage of 800kV and a rated power of 8000MW.
  • FIG. 4B is a diagram of simulation test results when an F1 ground fault occurs in the low-end converter on the rectifier side provided by the embodiment of the present application.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral line current
  • IDEL is the ground pole line current
  • POWER is the pole power
  • X_BLOCK_MC1 is the pole lock signal
  • BLK_RUN_U_PROT is the inverter lock.
  • BLOCK_IND_V1 is the high-end converter blocking signal
  • BLOCK_IND_V2 is the low-end converter blocking signal.
  • the UHV DC transmission system has a rated voltage of 800kV and a rated power of 8000MW.
  • the two poles are operated at rated power.
  • the converter differential protection is activated, the converter is blocked, the faulty converter is blocked, the low-end converter is blocked, and the BLOCK_IND_V2 is changed.
  • the current flowing through the fault point is equal to IDNC-IDL.
  • the peak current flowing through the fault point is 11661A; the electric quantity Q at the fault point: 0.30Ah; the I 2 t at the fault point: 1889.0A 2 h; the power loss at the fault point: 1600MW.
  • the method based on the present application can reduce the current flowing into the fault point, reduce the current flowing into the ground electrode circuit, and reduce the DC power loss.
  • Fig. 5A is a graph of simulation test results when an F2 ground fault occurs in a low-end converter on the rectifier side of the prior art.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral line current
  • IDEL is the ground pole line current
  • POWER is the pole power
  • X_BLOCK_MC1 is the pole lock signal
  • BLK_RUN_U_PROT is the inverter lock.
  • BLOCK_IND_V1 is the high-end converter blocking signal
  • BLOCK_IND_V2 is the low-end converter blocking signal.
  • the UHV DC transmission system has a rated voltage of 800kV and a rated power of 8000MW.
  • the two poles are operated at rated power.
  • the converter differential protection will act, perform pole blocking, X_BLOCK_MC1 displacement, and block the entire DC pole.
  • the current flowing through the fault point is equal to IDNC-IDL.
  • the peak current flowing through the fault point is 10911A; the electric quantity Q at the fault point: 0.46Ah; the I 2 t at the fault point: 2671.4A 2 h; the power loss at the fault point: 4000MW.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral line current
  • IDEL is the ground pole line current
  • POWER is the pole power
  • X_BLOCK_MC1 is the pole lock signal
  • BLK_RUN_U_PROT is the inverter lock.
  • BLOCK_IND_V1 is the high-end converter blocking signal
  • BLOCK_IND_V2 is the low-end converter blocking signal.
  • the UHV DC transmission system has a rated voltage of 800kV and a rated power of 8000MW.
  • the two poles are operated at rated power.
  • the converter differential protection is activated, the converter is blocked, the faulty converter is blocked, the low-end converter is blocked, and the BLOCK_IND_V2 is changed.
  • the current flowing through the fault point is equal to IDNC-IDL.
  • the peak current flowing through the fault point is 11288A; the electric quantity Q at the fault point: 0.26Ah; the I 2 t at the fault point: 1568.5A 2 h; the power loss at the fault point: 1600MW.
  • FIG. 6 is a schematic structural diagram of a ground fault control device 300 for a valve zone of an UHV DC low-end converter provided by an embodiment of the present application, which includes a detection unit 310 and a control unit 320.
  • the detection unit 310 detects the high-voltage bus current IDC2P and low-voltage bus current IDC2N of the low-end converter, detects the bipolar neutral bus current IDNC, and detects the high-voltage bus current IDC1P, low-voltage bus current IDC1N or polar bus current of the high-end converter.
  • IDL detects the pole bus voltage UDL and the pole neutral bus voltage UDN.
  • control unit 320 determines that the UHV DC transmission system is operating in bipolar and the full valve group where the low-end converter is located, and detects that the valve area of the low-end converter has a ground fault, it controls the low-end converter At the same time, the bipolar DC current is controlled to be equal, and the low-end converter is isolated, and the remaining converters are controlled to continue to operate.

Abstract

本申请提供特高压直流低端换流器阀区接地故障控制方法及控制装置。所述控制方法及控制装置应用于特高压直流输电系统的直流极的低端换流器，所述特高压直流输电系统包括双直流极，所述直流极包括串联连接的至少两个换流器，所述低端换流器为靠近极中性母线的换流器，当所述特高压直流输电系统双直流极运行且所述低端换流器所在直流极为全阀组运行，并检测到所述低端换流器的阀区发生接地故障时，所述控制方法包括：控制所述低端换流器闭锁；控制所述特高压直流输电系统双直流极的直流电流相等；隔离所述低端换流器；除所述低端换流器之外的换流器继续运行。

Description

特高压直流低端换流器阀区接地故障控制方法及控制装置 技术领域
本申请涉及高压直流输电技术领域，具体涉及特高压直流低端换流器阀区接地故障控制方法及控制装置。
背景技术
特高压直流输电系统一般采用两个换流器串联组成一个直流极，根据现有的工程分为常规特高压直流输电系统、分层接入特高压直流输电系统和混合特高压直流输电系统。
常规特高压直流输电系统为一个直流极的高、低端换流器都为电网换相换流器，且接入同一个交流电网。分层接入特高压直流输电系统为一个直流极的高、低端换流器都为电网换相换流器，且分别接入两个不同的交流电网。混合特高压直流输电系统分为两种：站间混合、极间混合和极内混合，站间混合的混合特高压直流输电系统采用电压源换流器的换流站一个直流极的高、低端换流器都为电压源换流器，极间混合的混合特高压直流输电系统采用电压源换流器的直流极的高、低端换流器都为电压源换流器，极内混合的混合特高压直流输电系统采用电网换相换流器和电压源换流器的直流极的高、低端换流器分别为电网换相换流器和电压源换流器。
当特高压直流输电系统双极平衡运行时，换流器检测到换流器阀区接地故障时，现有技术通过闭锁整个直流极来隔离故障，故障隔离后，采用单极大地回线继续运行，或者转金属回线运行，或者通过重启直流极的非故障换流器来实现双极平衡运行。
现有技术主要存在以下几个问题：闭锁整个直流极后，接地极线将流过很大电流，容易导致附近变电站的变压器有直流偏磁，引起变压器饱和；闭锁整个直流极后，如果输送功率较大，会损失较多的直流功率；闭锁整个直流极后，故障点会流过更多的故障电流。
因此，当特高压直流输电系统双极平衡运行时，换流器检测到换流器阀区接地故障时，应尽量在某些工况下不闭锁整个直流极，而只是闭锁故障的换流器。
发明内容
本申请实施例提供一种特高压直流低端换流器阀区接地故障控制方法，应用于特高压直流输电系统的直流极的低端换流器，所述特高压直流输电系统包括双直流极，所述直流极包括串联连接的至少两个换流器，所述低端换流器为靠近极中性母线的换流器，当所述特高压直流输电系统双直流极运行且所述低端换流器所在直流极为全阀组运行，并检测到所述低端换流器的阀区发生接地故障时，所述控制方法包括：控制所述低端换流器闭锁；控制所述特高压直流输电系统双直流极的直流电流相等；隔离所述低端换流器；除所述低端换流器之外的换流器继续运行。
根据一些实施例，所述低端换流器包括电网换相换流器或电压源换流器中的至少一种。
根据一些实施例，所述双直流极运行包括：每个所述直流极有至少一个换流器在运行；所述全阀组运行包括：所述低端换流器所在直流极除所述低端换流器之外还至少有一个换流器在运行。
根据一些实施例，所述低端换流器的阀区发生接地故障，包括：所述低端换流器发生接地故障、所述低端换流器与换流变压器之间连接线发生接地故障、所述换流变压器阀侧绕组发生接地故障的至少一种。
根据一些实施例，所述检测到所述低端换流器的阀区发生接地故障，包括：检测到所述低端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
根据一些实施例，如果所述低端换流器为电压源换流器，所述控制所述低端换流器闭锁，包括：控制所述低端换流器停发触发脉冲，闭合所述低端换流器所在低端阀组的第二旁通开关，跳开所述低端换流器的换流变压器进线开关，所述第二旁通开关连接所述低端换流器的正极和负极。
根据一些实施例，如果所述低端换流器为电网换相换流器，所述控制所述低端换流器闭锁包括：当所述低端换流器整流运行时，选择整流侧换流器第一种闭锁方式或整流侧换流器第二种闭锁方式，控制所述低端换流器闭锁；当所述低端换流器逆变运行时，选择逆变侧换流器第一种闭锁方式或逆变侧换流器第二种闭锁方式，控制所述低端换流器闭锁。
根据一些实施例，所述整流侧换流器第一种闭锁方式包括：控制整流运行的所述低端换流器停发触发脉冲，相应的逆变运行的换流器控制触发角为90度；控制跳开所述低端换流器的换流变压器进线开关，闭合所述低端换流器的第二旁通开关，相应的逆变运行的换流器投入旁通对，合旁通开关，所述第二旁通开关连接所述低端换流器的阳极和阴极。
根据一些实施例，所述整流侧换流器第二种闭锁方式包括：控制所述低端换流器投入旁通对，闭合第二旁通开关，同时跳开所述低端换流器的换流变压器进线开关，相应的逆变运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；控制所述相应的逆变运行的换流器投入旁通对，闭合旁通开关。
根据一些实施例，所述逆变侧换流器第一种闭锁方式包括：控制跳开逆变运行的所述低端换流器的换流变压器进线开关，投入旁通对，合第二旁通开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；控制所述相应的整流运行的换流器投入旁通对，合旁通开关。
根据一些实施例，所述逆变侧换流器第二种闭锁方式包括：控制逆变运行的所述低端换流器投入旁通对，合第二旁通开关，同时跳开所述低端换流器的换流变压器进线开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；控制所述相应的整流运行的换流器投入旁通对，合旁通开关。
根据一些实施例，所述控制所述特高压直流输电系统双直流极的直流电流相等，包括：给定双直流极的换流器相同的直流电流参考值；控制除所述低端换流器之外的换流器的高压母线电流或低压母线电流或极母线电流为所述直流电流参考值；所述直流电流参考值根据特高压直流输电系统的有功功率、无功功率、故障电流限制或入地电流限制需求确定；如果发生故障的所述低端换流器整流运行时，整流侧的除所述低端换流器之外的换流器采用电流控制来控制整流侧除所述低端换流器之外的换流器直流电流相等，逆变侧的换流器 运行在最大触发角控制或直流电压控制；如果发生故障的所述低端换流器逆变运行时，逆变侧除所述低端换流器之外的换流器将故障信息发送到整流侧，整流侧控制双直流极的换流器直流电流相等，或者采用电流控制来控制逆变侧除所述低端换流器之外的换流器直流电流相等，整流侧的换流器运行在直流电压控制。
根据一些实施例，所述隔离所述低端换流器，包括：闭合所述低端换流器所在低端阀组的第一旁通开关，分开所述低端换流器所在低端阀组的第二旁通开关、阀组开关和母线开关，所述第一旁通开关与所述低端换流器并联连接，所述第二旁通开关连接所述低端换流器的两端，所述阀组开关连接所述低端换流器与阀组连接线，所述母线开关连接所述低端换流器与极中性母线。
根据一些实施例，如果所述第二旁通开关、阀组开关和母线开关的分断电流定值均小于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，所述隔离所述低端换流器，包括：如果所述低端换流器直流侧的高压母线电流大于低压母线电流，分开所述阀组开关，控制双直流极直流电流为零，再分开所述第二旁通开关，恢复双直流极直流电流，后分开所述母线开关；如果所述低端换流器直流侧的高压母线电流小于低压母线电流，分开所述母线开关，控制双直流极直流电流为零，再分开所述第二旁通开关，恢复双直流极直流电流，后分开所述阀组开关。
根据一些实施例，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述第二旁通开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述阀组开关，再分开所述第二旁通开关，后分开所述母线开关；如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述母线开关，再分开所述第二旁通开关，后分开所述阀组开关。
根据一些实施例，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述阀组开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述第二旁通开关，再分开所述阀组开关，后分开所述母线开关；如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述母线开关，再分开所述阀组开关，后分开所述第二旁通开关。
根据一些实施例，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述母线开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述阀组开关，再分开所述母线开关，后分开所述第二旁通开关；如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述第二旁通开关，再分开所述母线开关，后分开所述阀组开关。
根据一些实施例，所述除所述低端换流器之外的换流器继续运行，包括：所述低端换流器所在站除所述低端换流器之外的换流器继续运行，其他站退出与所述低端换流器相应 的换流器，剩余的换流器继续运行。
根据一些实施例，所述隔离所述低端换流器之前，还包括：增大所述低端换流器所在直流极的极差保护差动电流定值或者增大所述低端换流器所在直流极的极差保护延时定值或者屏蔽极差保护，直至所述低端换流器隔离。
根据一些实施例，所述控制所述低端换流器闭锁之后，还包括：拉开金属回线转换开关或中性母线接地开关来断开换流站与大地之间的连接，所述金属回线转换开关连接双极中性母线与接地极线路，所述中性母线接地开关连接双极中性母线与站内接地网。
根据一些实施例，如果拉开所述金属回线转换开关或中性母线接地开关，所述控制方法还包括：隔离所述低端换流器之后，闭合所述金属回线转换开关或所述中性母线接地开关。
本申请实施例还提供一种特高压直流低端换流器阀区接地故障控制装置，应用如上所述特高压直流低端换流器阀区接地故障控制方法，所述控制装置包括检测单元和控制单元，所述检测单元检测所述低端换流器的高压母线电流和低压母线电流，检测极中性母线电流，检测所述低端换流器所在极的除所述低端换流器之外的换流器的高压母线电流、低压母线电流或极母线电流，检测极母线电压和极中性母线电压；所述控制单元判断特高压直流输电系统在双直流极运行，且所述低端换流器所在直流极为全阀组运行并检测到所述低端换流器的阀区发生接地故障时，控制所述低端换流器闭锁，同时控制双直流极直流电流相等，隔离所述低端换流器，控制除所述低端换流器之外的换流器继续运行。
本申请实施例提供的技术方案，当特高压直流输电系统双直流极平衡运行时，低端换流器所在直流极为全阀组运行并检测到低端换流器阀区接地故障时，不闭锁整个直流极，而只是闭锁故障的低端换流器，通过双极平衡控制，将正常运行极的电流导入到故障极的极母线上，从而避免正常运行极的电流过多地流入到故障点，同时保证更多换流器运行，避免损失较大直流输送功率。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的一种特高压直流输电系统的主回路示意图。
图2是本申请实施例提供的一种特高压直流低端换流器阀区接地故障控制方法流程示意图。
图3是整流侧低端换流器的阀区接地故障位置示意图。
图4A是现有技术整流侧低端换流器发生F1接地故障时的仿真试验结果图。
图4B是本申请实施例提供的整流侧低端换流器发生F1接地故障时的仿真试验结果图。
图5A是现有技术整流侧低端换流器发生F2接地故障时的仿真试验结果图。
图5B是本申请实施例提供的整流侧低端换流器发生F2接地故障时的仿真试验结果图。
图6是本申请实施例提供的一种特高压直流低端换流器阀区接地故障控制装置的结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
应当理解，本申请的权利要求、说明书及附图中的术语“第一”、“第二”、“第三”、“第四”等是用于区别不同对象，而不是用于描述特定顺序。本申请的说明书和权利要求书中使用的术语“包括”指示所描述特征、整体、步骤、操作、元素和/或组件的存在，但并不排除一个或多个其它特征、整体、步骤、操作、元素、组件和/或其集合的存在或添加。
图1是本申请实施例提供的一种特高压直流输电系统的主回路示意图。
特高压直流输电系统主回路包括整流站100、逆变站200、第一直流线路150、第二直流线路160、整流站接地极线路114、整流站接地极115和逆变站接地极线路214、逆变站接地极215。
整流站100包括第一直流极I110、第二直流极II120、第一交流滤波器组118、第一交流系统140及换流变压器进线开关和金属回线转换开关113。
第一直流极I110包括第一高端阀组111、第一低端阀组112、第一高端换流变压器116、第一低端换流变压器117、第一直流滤波器93和第一平波电抗器91。第一高端阀组111和第一低端阀组112为串联连接。
第一高端阀组111包括第一高端换流器1、第一高端阀组第一旁通开关11、第一高端阀组第二旁通开关12、第一高端阀组母线开关13、第一高端阀组阀组开关14。第一高端阀组第一旁通开关11与第一高端换流器1并联连接。第一高端阀组第二旁通开关12连接第一高端换流器1的两端。第一高端阀组阀组开关14连接第一高端换流器1与阀组连接线。第一高端阀组母线开关13连接第一高端换流器1与极母线。
第一低端阀组112包括第一低端换流器2、第一低端阀组第一旁通开关21、第一低端阀组第二旁通开关22、第一低端阀组阀组开关23、第一低端阀组母线开关24。第一低端阀组第一旁通开关21与第一低端换流器2并联连接，第一低端阀组第二旁通开关22连接第三低端换流器6的两端，第一低端阀组阀组开关23连接第一低端换流器2与阀组连接线，第一低端阀组母线开关24连接第一低端换流器2与极中性母线。
第一高端换流器1和第一低端换流器2包括电网换相换流器或电压源换流器的至少一种。
电网换相换流器包括但不限于六脉动桥式电路、十二脉动桥式电路的至少一种。所述脉动桥式电路包括但不限于不可关断的半控型功率半导体器件，一般为晶闸管器件。
电压源换流器包括但不限于两电平换流器、二极管箝位型多电平换流器、模块化多电平换 流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种，所述换流器包括但不限于可关断的全控型功率半导体器件。上述模块化多电平换流器MMC包括但不限于半桥子模块结构的模块化多电平换流器MMC、全桥子模块结构的模块化多电平换流器MMC、半桥和全桥混合子模块结构的模块化多电平换流器MMC的至少一种。
第二直流极II120包括第二低端阀组121、第二高端阀组122、第二低端换流变压器126、第二高端换流变压器127、第二直流滤波器94和第二平波电抗器92。第二低端阀组121和第二高端阀组122为串联连接。
第二高端阀组122包括第二高端换流器4、第二高端阀组第一旁通开关41、第二高端阀组第二旁通开关42、第二高端阀组阀组开关43、第二高端阀组母线开关44。第二高端阀组第一旁通开关41与第二高端换流器4并联连接，第二高端阀组第二旁通开关42连接第二高端换流器4的两端，第二高端阀组阀组开关43连接第二高端换流器4与阀组连接线，第二高端阀组母线开关44连接第二高端换流器4与极母线。
第二低端阀组121包括第二低端换流器3、第二低端阀组第一旁通开关31、第二低端阀组第二旁通开关32、第二低端阀组母线开关33、第二低端阀组阀组开关34。第二低端阀组第一旁通开关31与第二低端换流器3并联连接，第二低端阀组第二旁通开关32连接第二低端换流器3的两端，第二低端阀组阀组开关34连接第二低端换流器3与阀组连接线，第二低端阀组母线开关33连接第二低端换流器3与极中性母线。
第二高端换流器4和第二低端换流器3包括电网换相换流器或电压源换流器的至少一种。
逆变站200包括第三直流极I210、第四直流极II220、第二交流滤波器组218和第二交流系统240及换流变压器进线开关。
第三直流极I210包括第三高端阀组211、第三低端阀组212、第三高端换流变压器216、第三低端换流变压器217、第三直流滤波器97和第三平波电抗器95。第三高端阀组211和第三低端阀组212为串联连接。
第三高端阀组211包括第三高端换流器5、第三高端阀组第一旁通开关51、第三高端阀组第二旁通开关52、第三高端阀组母线开关53、第三高端阀组阀组开关54。第三高端阀组第一旁通开关51与第三高端换流器5并联连接，第三高端阀组第二旁通开关52连接第三高端换流器5的两端，第三高端阀组阀组开关54连接第三高端换流器5与阀组连接线，第三高端阀组母线开关53连接第三高端换流器5与极母线。
第三低端阀组212包括第三低端换流器6、第三低端阀组第一旁通开关61、第三低端阀组第二旁通开关62、第三低端阀组阀组开关63、第三低端阀组母线开关64。第三低端阀组第一旁通开关61与第三低端换流器6并联连接，第三低端阀组第二旁通开关62连接第三低端换流器6的两端，第三低端阀组阀组开关63连接第三低端换流器6与阀组连接线，第三低端阀组母线开关64连接第三低端换流器6与极中性母线。
第三高端换流器5和第三低端换流器6包括电网换相换流器或电压源换流器的至少一种。
第四直流极II220包括第四低端阀组221、第四高端阀组222、第四低端换流变压器226、第四高端换流变压器227、第二直流滤波器98和第二平波电抗器96。第四低端阀组221和第四高端阀组222为串联连接。
第四高端阀组222包括第四高端换流器8、第四高端阀组第一旁通开关81、第四高端阀组第二旁通开关82、第四高端阀组阀组开关83、第四高端阀组母线开关84。第四高端阀组第一旁通开关81与第四高端换流器8并联连接，第四高端阀组第二旁通开关82连接第四高端换流器8的两端，第四高端阀组阀组开关83连接第四高端换流器8与阀组连接线，第四高端阀组母线开关84连接第四高端换流器8与极母线。
第四低端阀组221包括第四低端换流器7、第四低端阀组第一旁通开关71、第四低端阀组第二旁通开关72、第四低端阀组母线开关73、第四低端阀组阀组开关74。第四低端阀组第一旁通开关71与第四低端换流器7并联连接，第四低端阀组第二旁通开关72连接第四低端换流器7的两端，第四低端阀组阀组开关74连接第四高端换流器7与阀组连接线，第四低端阀组母线开关73连接第四低端换流器7与极中性母线。
第四高端换流器8和第四低端换流器7包括电网换相换流器或电压源换流器的至少一种。
上述提到的各种开关，包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。
如果整流站100和逆变站200的直流极的高端换流器和低端换流器都为电网换相换流器，高端换流器和低端换流器连接同一个交流电网，则为常规特高压直流输电系统。
如果整流站100和逆变站200的直流极的高端换流器和低端换流器都为电网换相换流器，高端换流器和低端换流器连接不同交流电网，则为分层接入特高压直流输电系统。
如果整流站100的第一直流极I110和第二直流极II120的第一高端换流器1、第一低端换流器2、第二高端换流器4和第二低端换流器3都为电网换相换流器，逆变站200的第三直流极I210和第四直流极II220的第三高端换流器5、第三低端换流器6、第四高端换流器8和第四低端换流器7都为电压源换流器，则为站间混合的混合特高压直流输电系统。
如果整流站100的第一直流极I110和第二直流极II120的第一高端换流器1、第一低端换流器2、第二高端换流器4和第二低端换流器3都为电网换相换流器，逆变站200的第三直流极I210和第四直流极II220的第三高端换流器5和第四高端换流器8为电网换相换流器，第三低端换流器6和第四低端换流器7为电压源换流器，则为极内混合的混合特高压直流输电系统。
整流站100通过接地极线路114与接地极115连接。逆变站200通过接地极线路214与接地极215连接。功率正送时，整流站100的第一交流系统140通过其第一高端换流器1、第一低端换流器2、第二高端换流器4和第二低端换流器3将交流电转化为直流电，通过直流线路150、160输送到逆变站200，逆变站200通过其第三高端换流器5、第三低端换流器6、第四高端换流器8和第四低端换流器7将直流电转化为交流电送到逆变站200的第二交流系统240，从而实现直流功率正送。整流站的换流器一般运行在电流控制，逆变站的换流器一般运行在电压控制或最大触发角控制(AMAX)。需要指出的是，最大触发角控制(AMAX)仅适用于电网换相换流器，不适用于电压源换流器。
整流站100和逆变站200采集的模拟量信号为：高端换流器直流侧的高压母线电流IDC1P、低压母线电流IDC1N，低端换流器直流侧的高压母线电流IDC2P、低压母线电流IDC2N，极中性母线电流IDNC，极母线电流IDL，接地极线路电流IDEL，极母线电压UDL和极中性母线电压UDN。
图2是本申请实施例提供的一种特高压直流低端换流器阀区接地故障控制方法流程示意图。
特高压直流输电系统包括双直流极，直流极包括串联连接的至少两个换流器，低端换流器为靠近极中性母线的换流器。以下为技术术语定义。
双直流极运行：每个直流极有至少一个换流器在运行。
全阀组运行：直流极至少有两个换流器在运行。
低端换流器的阀区发生接地故障：包括低端换流器发生接地故障、低端换流器与换流变压器之间连接线发生接地故障、换流变压器阀侧绕组发生接地故障的至少一种。
检测到低端换流器的阀区发生接地故障：检测到低端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
低端换流器的阀区发生接地故障通过换流器差动保护动作来判断，换流器差动保护动作判据公式如下。
IDiff_v＝|IDC2P–IDC2N|，
IRes_v＝|IDC2P+IDC2N|/2，
IDiff_v>max(Iv_set,kv_set*IRes_v)；
其中，IDC2P为低端换流器直流侧的高压母线电流，IDC2N为低端换流器直流侧的低压母线电流，Iv_set为起动电流定值，kv_set为比率系数。
当特高压直流输电系统双直流极运行且低端换流器所在直流极为全阀组运行，即一直流极的高端换流器和低端换流器同时运行并且另一直流极至少有一个换流器在运行，所述一直流极的低端换流器检测到低端换流器的阀区发生接地故障时，控制方法如下。
在S110中，控制低端换流器闭锁。
如果低端换流器为电压源换流器，控制低端换流器闭锁为立即停发触发脉冲，闭合低端换流器所在阀组的第二旁通开关，跳开低端换流器的换流变压器进线开关，第二旁通开关连接低端换流器的正极和负极。
以第一低端换流器2为例，如果第一低端换流器2为电压源换流器，控制第一低端换流器2闭锁为立即停发触发脉冲，闭合第一低端阀组第二旁通开关22，跳开第一低端换流器2的第一低端换流变压器进线开关132，第一低端阀组第二旁通开关22连接第一低端换流器2的正极和负极。
如果低端换流器为电网换相换流器，控制低端换流器闭锁根据运行于整流或逆变状态选择不同的闭锁方式，当低端换流器整流运行时，选择以下两种闭锁方式的任一种：整流侧换流器第一种闭锁方式和整流侧换流器第二种闭锁方式。当低端换流器逆变运行时，选择以下两种闭锁方式的任一种：逆变侧换流器第一种闭锁方式和逆变侧换流器第二种闭锁方式。
以整流站100为例，如果第一直流极I110的第一低端换流器2整流运行，如果采用整流侧换流器第一种闭锁方式：整流站100第一直流极I110的第一低端换流器2立即停发触发脉冲，逆变站200第三直流极I210的第三低端换流器6控制触发角为90度；整流站100第一直 流极I110的第一低端换流器2跳开第一低端换流变压器进线开关132，闭合第一低端阀组第二旁通开关22，逆变站200第三直流极I210的第三低端换流器6投入旁通对，闭合第三低端阀组第二旁通开关62。
以整流站100为例，如果第一直流极I110的第一低端换流器2整流运行，如果采用整流侧换流器第二种闭锁方式：整流站100第一直流极I110的第一低端换流器2投入旁通对，闭合第一低端阀组第二旁通开关22，同时跳开第一低端换流变压器进线开关132，逆变站200第三直流极I210的第三低端换流器6控制触发角为90度；逆变站200第三直流极I210的第三低端换流器6投入旁通对，闭合第三低端阀组第二旁通开关62。
以逆变站200为例，如果第三直流极I210的第三低端换流器6逆变运行，如果采用逆变侧换流器第一种闭锁方式：逆变站200第三直流极I210的第三低端换流器6跳开第三低端换流变压器进线开关232，第三低端换流变压器进线开关232跳开后投入旁通对，闭合第三低端阀组第二旁通开关62，整流站100第一直流极I110的第一低端换流器2控制触发角为90度；整流站100第一直流极I110的第一低端换流器2投入旁通对，闭合第一低端阀组第二旁通开关22。
以逆变站200为例，如果第三直流极I210的第三低端换流器6逆变运行，如果采用逆变侧换流器第二种闭锁方式：逆变站200极I210的第三低端换流器6投入旁通对，闭合第三低端阀组第二旁通开关62，同时跳开第三低端换流变压器进线开关232，整流站100第一直流极I110的第一低端换流器2控制触发角为90度；整流站100第一直流极I110的第一低端换流器2投入旁通对，闭合第一低端阀组第二旁通开关22。
在S120中，控制特高压直流输电系统双直流极的直流电流相等。
控制双极直流电流相等是通过控制双直流极的换流器的直流电流为相同的直流电流参考值。双直流极的直流电流或换流器的直流电流为除故障的低端换流器外的换流器直流侧的高压母线电流、低压母线电流或极母线电流。
直流电流参考值根据特高压直流输电系统的有功功率、无功功率、故障电流限制或入地电流限制需求确定。
如果故障发生在整流站100第一直流极I110的第一低端换流器2时，控制第一高端换流器1的直流电流与第二直流极II120的换流器的直流电流相等，逆变站200第三直流极I210的第三高端换流器5或第三低端换流器6控制直流电压或控制最大触发角。
如果故障发生在逆变站200第三直流极I210的第三低端换流器6时，将故障信息传送到整流站100，控制整流站100第一直流极I110的第一高端换流器1或第一低端换流器2的直流电流与第二直流极II120的换流器的直流电流相等，逆变站200第三直流极I210的第三高端换流器5控制直流电压或控制最大触发角。
在S130中，隔离低端换流器。
以第一低端换流器2故障为例，隔离第一低端换流器2，闭合第一低端阀组第一旁通开关21，分开第一低端阀组第二旁通开关22和第一低端阀组阀组开关23、第一低端阀组母线开关24。
第一低端阀组第一旁通开关21与第一低端换流器2并联连接，第一低端阀组第二旁通 开关22连接第一低端换流器2的两端，第一低端阀组阀组开关23连接第一低端换流器2与阀组连接线，第一低端阀组母线开关24连接第一低端换流器2与极中性母线。
如果第一低端阀组第二旁通开关22、第一低端阀组开关23和第一低端阀组母线开关24的分断电流定值均小于第一低端换流器2直流侧的高压母线电流IDC2P或者低压母线电流IDC2N中的较大值，那么按照如下两种情况隔离低端换流器2。
第一种，如果第一低端换流器2直流侧的高压母线电流IDC2P大于低压母线电流IDC2N，分开第一低端阀组阀组开关23，控制双直流极的直流电流为零，再分开第一低端阀组第二旁通开关22，恢复双直流极直流电流为正常值，后分开第一低端阀组母线开关24。
第二种，如果第一低端换流器2直流侧的高压母线电流IDC2P小于低压母线电流IDC2N，分开第一低端阀组母线开关24，控制双直流极直流电流为零，再分开第一低端阀组第二旁通开关22，恢复双直流极直流电流，后分开第一低端阀组阀组开关23。
如果第一低端阀组第二旁通开关22、第一低端阀组阀组开关23和第一低端阀组母线开关24中任一个的分断电流定值大于低端换流器2直流侧的高压母线电流IDC2P或者低压母线电流IDC2N中的较大值，按照以下几种情况隔离低端换流器。
如果第一低端阀组第二旁通开关22的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P大于低压母线电流IDC2N，先分开第一低端阀组阀组开关23，再分开第一低端阀组第二旁通开关22，后分开第一低端阀组母线开关24。
如果第一低端阀组第二旁通开关22的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P小于低压母线电流IDC2N，先分开第一低端阀组母线开关24，再分开第一低端阀组第二旁通开关22，后分开第一低端阀组阀组开关23。
如果第一低端阀组第一阀组阀组开关23的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P大于低压母线电流IDC2N，先分开第一低端阀组第二旁通开关22，再分开第一低端阀组阀组开关23，后分开第一低端阀组母线开关24。
如果第一低端阀组第一阀组阀组开关23的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P小于低压母线电流IDC2N，先分开第一低端阀组母线开关24，再分开第一低端阀组阀组开关23，后分开第一低端阀组第二旁通开关22。
如果第一低端阀组第一母线开关24的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P大于低压母线电流IDC2N，先分开第一低端阀组阀组开关23，再分开第一低端阀组母线开关24，后分开第一低端阀组第二旁通开关22。
如果第一低端阀组第一母线开关24的分断电流定值最大，且第一低端换流器2直流侧的高压母线电流IDC2P小于低压母线电流IDC2N，先分开第一低端阀组第二旁通开关22，再分开第一低端阀组母线开关24，后分开第一低端阀组阀组开关23。
在S140中，除低端换流器之外的换流器继续运行。
剩余的换流器继续运行为整流站100的第一直流极I110的第一高端换流器1，第二直流极II120的第二高端换流器4和第二低端换流器3继续运行，逆变站200退出第三直流极I210的第三低端换流器6，第三直流极I210的第三高端换流器5，第四直流极II220的第四高端换流器8和第四低端换流器7继续运行。
为了防止其他保护动作，此种情况下，低端换流器检测到低端换流器的阀区发生接地故障时，增大低端换流器所在直流极的极差保护差动电流定值或者增大低端换流器所在直流极的极差保护延时定值或者屏蔽极差保护，屏蔽阀组连接线差动保护，低端换流器隔离后，再开放极差保护、阀组连接线差动保护。
极差保护差动电流为极中性母线电流、直流滤波器电流、极中性母线冲击电容器电流和极中性母线避雷器电流之和与极母线电流之差。阀组连接线差动电流为高端换流器直流侧的低压母线电流与低端换流器直流侧的高压母线电流之差。
如果整流站100在双极大地回线运行，采用接地极线路接地，即金属回线转换开关113处于合位，其第一低端换流器2发生故障，上述控制第一低端换流器2闭锁后，可选地，拉开金属回线转换开关113来断开换流站与大地之间的正常连接，如果双直流极平衡运行，此时故障点将不会流过电流。如果逆变站200配置金属回线转换开关，也可采用相同方法来快速隔离故障电流。上述隔离第一低端换流器2后，重新合上金属回线转换开关113。
本实施例提供的技术方案，当特高压直流输电系统双直流极平衡运行时，低端换流器所在直流极为全阀组运行并检测到低端换流器阀区接地故障时，不闭锁整个直流极，而只是闭锁故障的低端换流器，通过双极平衡控制，将正常运行极的电流导入到故障极的极母线上，从而避免正常运行极的电流过多地流入到故障点，同时保证更多换流器运行，避免损失较大直流输送功率。
图3所示为整流侧低端换流器的阀区发生接地故障位置。F1属于低端换流器发生接地故障。F2属于低端换流器与换流变压器之间连接线发生接地故障。
图4A是现有技术整流侧低端换流器发生F1接地故障时的仿真试验结果图。
图4A所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，POWER为极功率，X_BLOCK_MC1为执行极闭锁信号，BLK_RUN_U_PROT为执行换流器闭锁信号，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW。
故障前双极以额定功率运行，当检测到发生F1接地故障时，换流器差动保护动作，执行极闭锁，X_BLOCK_MC1变位，闭锁整个直流极，高端换流器和低端换流器都闭锁，BLOCK_IND_V1变位，BLOCK_IND_V2变位。故障点流过的电流等于IDNC-IDL。故障点流过的峰值电流为12032A；故障点的电量Q：1.70Ah；故障点的I 2t：8830.3A 2h；故障极损失功率：4000MW。
图4B是本申请实施例提供的整流侧低端换流器发生F1接地故障时的仿真试验结果图。
图4B所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，POWER为极功率，X_BLOCK_MC1为执行极闭锁信号，BLK_RUN_U_PROT为执行换流器闭锁信号，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW。
故障前双极以额定功率运行，当检测到发生F1接地故障时，换流器差动保护动作，执行换流器闭锁，闭锁故障的换流器，低端换流器闭锁，BLOCK_IND_V2变位。故障点流过 的电流等于IDNC-IDL。故障点流过的峰值电流为11661A；故障点的电量Q：0.30Ah；故障点的I 2t：1889.0A 2h；故障极损失功率：1600MW。
通过对比图4A和图4B，可知基于本申请的方法可减少流入故障点的电流，减少流入接地极线路的电流，减少直流功率损失。
图5A是现有技术整流侧低端换流器发生F2接地故障时的仿真试验结果图。
图5A所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，POWER为极功率，X_BLOCK_MC1为执行极闭锁信号，BLK_RUN_U_PROT为执行换流器闭锁信号，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW。
故障前双极以额定功率运行，当检测到发生F1接地故障时，换流器差动保护动作，执行极闭锁，X_BLOCK_MC1变位，闭锁整个直流极，高端换流器和低端换流器都闭锁，BLOCK_IND_V1变位，BLOCK_IND_V2变位。故障点流过的电流等于IDNC-IDL。故障点流过的峰值电流为10911A；故障点的电量Q：0.46Ah；故障点的I 2t：2671.4A 2h；故障极损失功率：4000MW。
图5B是本申请实施例提供的整流侧低端换流器发生F2接地故障时的仿真试验结果图。
图5B所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，POWER为极功率，X_BLOCK_MC1为执行极闭锁信号，BLK_RUN_U_PROT为执行换流器闭锁信号，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW。
故障前双极以额定功率运行，当检测到发生F1接地故障时，换流器差动保护动作，执行换流器闭锁，闭锁故障的换流器，低端换流器闭锁，BLOCK_IND_V2变位。故障点流过的电流等于IDNC-IDL。故障点流过的峰值电流为11288A；故障点的电量Q：0.26Ah；故障点的I 2t：1568.5A 2h；故障极损失功率：1600MW。通过对比图5A和图5B，可知基于本申请的方法可减少流入故障点的电流，减少流入接地极线路的电流，减少直流功率损失。
图6是本申请实施例提供的一种特高压直流低端换流器阀区接地故障控制装置300的结构示意图，包括检测单元310和控制单元320。
检测单元310检测低端换流器的高压母线电流IDC2P和低压母线电流IDC2N，检测双极的极中性母线电流IDNC，检测高端换流器的高压母线电流IDC1P、低压母线电流IDC1N或极母线电流IDL，检测极母线电压UDL和极中性母线电压UDN。
控制单元320判断特高压直流输电系统在双极运行，且低端换流器所在极为全阀组运行并检测到所述低端换流器的阀区发生接地故障时，控制低端换流器闭锁，同时控制双极直流电流相等，隔离低端换流器，控制剩余的换流器继续运行。
以上对本申请实施例进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明仅用于帮助理解本申请的方法及其核心思想。同时， 本领域技术人员依据本申请的思想，基于本申请的具体实施方式及应用范围上做出的改变或变形之处，都属于本申请保护的范围。综上所述，本说明书内容不应理解为对本申请的限制。

Claims (22)

  1. 一种特高压直流低端换流器阀区接地故障控制方法，应用于特高压直流输电系统的直流极的低端换流器，所述特高压直流输电系统包括双直流极，所述直流极包括串联连接的至少两个换流器，所述低端换流器为靠近极中性母线的换流器，当所述特高压直流输电系统双直流极运行且所述低端换流器所在直流极为全阀组运行，并检测到所述低端换流器的阀区发生接地故障时，所述控制方法包括：
    控制所述低端换流器闭锁；
    控制所述特高压直流输电系统双直流极的直流电流相等；
    隔离所述低端换流器；
    除所述低端换流器之外的换流器继续运行。
  2. 如权利要求1所述的控制方法，其中，所述低端换流器包括电网换相换流器或电压源换流器中的至少一种。
  3. 如权利要求2所述的控制方法，其中，
    所述双直流极运行包括：每个所述直流极有至少一个换流器在运行；
    所述全阀组运行包括：所述低端换流器所在直流极除所述低端换流器之外还至少有一个换流器在运行。
  4. 如权利要求1所述的控制方法，其中，所述低端换流器的阀区发生接地故障，包括：
    所述低端换流器发生接地故障、所述低端换流器与换流变压器之间连接线发生接地故障、所述换流变压器阀侧绕组发生接地故障的至少一种。
  5. 如权利要求1所述的控制方法，其中，所述检测到所述低端换流器的阀区发生接地故障，包括：
    检测到所述低端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
  6. 如权利要求1所述的控制方法，其中，如果所述低端换流器为电压源换流器，所述控制所述低端换流器闭锁，包括：
    控制所述低端换流器停发触发脉冲，闭合所述低端换流器所在低端阀组的第二旁通开关，跳开所述低端换流器的换流变压器进线开关，所述第二旁通开关连接所述低端换流器的正极和负极。
  7. 如权利要求1所述的控制方法，其中，如果所述低端换流器为电网换相换流器，所述控制所述低端换流器闭锁包括：
    当所述低端换流器整流运行时，选择整流侧换流器第一种闭锁方式或整流侧换流器第二种闭锁方式，控制所述低端换流器闭锁；
    当所述低端换流器逆变运行时，选择逆变侧换流器第一种闭锁方式或逆变侧换流器第 二种闭锁方式，控制所述低端换流器闭锁。
  8. 如权利要求7所述的控制方法，其中，所述整流侧换流器第一种闭锁方式包括：
    控制整流运行的所述低端换流器停发触发脉冲，相应的逆变运行的换流器控制触发角为90度；
    控制跳开所述低端换流器的换流变压器进线开关，闭合所述低端换流器的第二旁通开关，相应的逆变运行的换流器投入旁通对，闭合旁通开关，所述第二旁通开关连接所述低端换流器的阳极和阴极。
  9. 如权利要求7所述的控制方法，其中，所述整流侧换流器第二种闭锁方式包括：
    控制所述低端换流器投入旁通对，闭合第二旁通开关，同时跳开所述低端换流器的换流变压器进线开关，相应的逆变运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；
    控制所述相应的逆变运行的换流器投入旁通对，闭合旁通开关。
  10. 如权利要求7所述的控制方法，其中，所述逆变侧换流器第一种闭锁方式包括：
    控制跳开逆变运行的所述低端换流器的换流变压器进线开关，投入旁通对，闭合第二旁通开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；
    控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
  11. 如权利要求7所述的控制方法，其中，所述逆变侧换流器第二种闭锁方式包括：
    控制逆变运行的所述低端换流器投入旁通对，闭合第二旁通开关，同时跳开所述低端换流器的换流变压器进线开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；
    控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
  12. 如权利要求1所述的控制方法，其中，所述控制所述特高压直流输电系统双直流极的直流电流相等，包括：
    给定双直流极的换流器相同的直流电流参考值；
    控制除所述低端换流器之外的换流器的高压母线电流或低压母线电流或极母线电流为所述直流电流参考值；
    所述直流电流参考值根据特高压直流输电系统的有功功率、无功功率、故障电流限制或入地电流限制需求确定；
    如果发生故障的所述低端换流器整流运行时，整流侧的除所述低端换流器之外的换流器采用电流控制来控制整流侧除所述低端换流器之外的换流器直流电流相等，逆变侧的换流器运行在最大触发角控制或直流电压控制；
    如果发生故障的所述低端换流器逆变运行时，逆变侧除所述低端换流器之外的换流器将故障信息发送到整流侧，整流侧控制双直流极的换流器直流电流相等，或者采用电流控制来控制逆变侧除所述低端换流器之外的换流器直流电流相等，整流侧的换流器运行在直 流电压控制。
  13. 如权利要求1所述的控制方法，其中，所述隔离所述低端换流器，包括：
    闭合所述低端换流器所在低端阀组的第一旁通开关，分开所述低端换流器所在低端阀组的第二旁通开关、阀组开关和母线开关，所述第一旁通开关与所述低端换流器并联连接，所述第二旁通开关连接所述低端换流器的两端，所述阀组开关连接所述低端换流器与阀组连接线，所述母线开关连接所述低端换流器与极中性母线。
  14. 如权利要求13所述的控制方法，其中，如果所述第二旁通开关、阀组开关和母线开关的分断电流定值均小于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，所述隔离所述低端换流器，包括：
    如果所述低端换流器直流侧的高压母线电流大于低压母线电流，分开所述阀组开关，控制双直流极直流电流为零，再分开所述第二旁通开关，恢复双直流极直流电流，后分开所述母线开关；
    如果所述低端换流器直流侧的高压母线电流小于低压母线电流，分开所述母线开关，控制双直流极直流电流为零，再分开所述第二旁通开关，恢复双直流极直流电流，后分开所述阀组开关。
  15. 如权利要求13所述的控制方法，其中，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述第二旁通开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：
    如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述阀组开关，再分开所述第二旁通开关，后分开所述母线开关；
    如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述母线开关，再分开所述第二旁通开关，后分开所述阀组开关。
  16. 如权利要求13所述的控制方法，其中，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述阀组开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：
    如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述第二旁通开关，再分开所述阀组开关，后分开所述母线开关；
    如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述母线开关，再分开所述阀组开关，后分开所述第二旁通开关。
  17. 如权利要求13所述的控制方法，其中，如果所述第二旁通开关、阀组开关和母线开关中任一个的分断电流定值大于所述低端换流器直流侧的高压母线电流或者低压母线电流中的较大值，且所述母线开关的分断电流定值最大，所述分开所述低端换流器的第二旁通开关、阀组开关和母线开关，包括：
    如果所述低端换流器直流侧的高压母线电流大于低压母线电流，先分开所述阀组开关，再分开所述母线开关，后分开所述第二旁通开关；
    如果所述低端换流器直流侧的高压母线电流小于低压母线电流，先分开所述第二旁通开关，再分开所述母线开关，后分开所述阀组开关。
  18. 如权利要求1所述的控制方法，其中，所述除所述低端换流器之外的换流器继续运行，包括：
    所述低端换流器所在站除所述低端换流器之外的换流器继续运行，其他站退出与所述低端换流器相应的换流器，剩余的换流器继续运行。
  19. 如权利要求1所述的控制方法，所述隔离所述低端换流器之前，还包括：
    增大所述低端换流器所在直流极的极差保护差动电流定值或者增大所述低端换流器所在直流极的极差保护延时定值或者屏蔽极差保护，直至所述低端换流器隔离。
  20. 如权利要求1所述的控制方法，其中，所述控制所述低端换流器闭锁之后，还包括：
    拉开金属回线转换开关或中性母线接地开关来断开换流站与大地之间的连接，所述金属回线转换开关连接双极中性母线与接地极线路，所述中性母线接地开关连接双极中性母线与站内接地网。
  21. 如权利要求20所述的控制方法，其中，如果拉开站内的所述金属回线转换开关或中性母线接地开关，所述控制方法还包括：
    隔离所述低端换流器之后，闭合所述金属回线转换开关或所述中性母线接地开关。
  22. 一种特高压直流低端换流器阀区接地故障控制装置，应用如权利要求1至21之任一项所述特高压直流低端换流器阀区接地故障控制方法，所述控制装置包括：
    检测单元，检测所述低端换流器的高压母线电流和低压母线电流，检测极中性母线电流，检测所述低端换流器所在极的除所述低端换流器之外的换流器的高压母线电流、低压母线电流或极母线电流，检测极母线电压和极中性母线电压；
    控制单元，判断特高压直流输电系统在双直流极运行，且所述低端换流器所在直流极为全阀组运行并检测到所述低端换流器的阀区发生接地故障时，控制所述低端换流器闭锁，同时控制双直流极直流电流相等，隔离所述低端换流器，控制除所述低端换流器之外的换流器继续运行。
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CN113054679B (zh) * 2019-12-26 2022-07-22 南京南瑞继保电气有限公司 高压直流输电系统直流侧接地故障控制方法及控制装置
CN110970879B (zh) * 2019-12-26 2021-10-01 南京南瑞继保电气有限公司 特高压直流低端换流器阀区接地故障控制方法及控制装置
CN111541259B (zh) * 2020-04-23 2021-07-30 南方电网科学研究院有限责任公司 混合多端直流输电系统的充电控制方法、装置和介质
CN111697610B (zh) * 2020-05-19 2021-11-19 南方电网科学研究院有限责任公司 三端直流输电系统的双极平衡控制方法、装置和介质
CN114374214B (zh) * 2020-10-15 2023-05-05 许继电气股份有限公司 一种特高压混合直流输电系统暂态电压控制方法及装置
CN113471918B (zh) * 2021-06-28 2022-12-13 南京南瑞继保电气有限公司 特高压直流输电系统融冰电路及其控制方法、控制装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130193766A1 (en) * 2012-01-31 2013-08-01 Atlantic Grid Operations A., Llc Control and protection of a dc power grid
CN104242292A (zh) * 2014-10-09 2014-12-24 南方电网科学研究院有限责任公司 一种直流工程无接地极方式运行的控制保护处理方法
CN105162155A (zh) * 2015-08-26 2015-12-16 浙江大学 一种具有直流故障穿越能力的串联混合型双极直流输电系统
CN107231085A (zh) * 2017-04-07 2017-10-03 中国矿业大学 一种基于直流母线双极等电位的mmc‑hvdc直流短路故障穿越方法
CN108199571A (zh) * 2018-03-05 2018-06-22 南京南瑞继保电气有限公司 一种换流器保护电路和保护方法及装置
CN110970879A (zh) * 2019-12-26 2020-04-07 南京南瑞继保电气有限公司 特高压直流低端换流器阀区接地故障控制方法及控制装置

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2590314A1 (de) * 2011-11-03 2013-05-08 ABB Technology AG Umrichtersystem sowie leistungselektronisches System mit solchen Umrichtersystemen
CN104362660B (zh) * 2014-10-11 2016-11-30 中国南方电网有限责任公司 高压直流输电系统站内接地方式的双极运行方法
CN105470923B (zh) * 2015-12-31 2018-05-15 国家电网公司 增加特高压换流站换流器保护区域的方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130193766A1 (en) * 2012-01-31 2013-08-01 Atlantic Grid Operations A., Llc Control and protection of a dc power grid
CN104242292A (zh) * 2014-10-09 2014-12-24 南方电网科学研究院有限责任公司 一种直流工程无接地极方式运行的控制保护处理方法
CN105162155A (zh) * 2015-08-26 2015-12-16 浙江大学 一种具有直流故障穿越能力的串联混合型双极直流输电系统
CN107231085A (zh) * 2017-04-07 2017-10-03 中国矿业大学 一种基于直流母线双极等电位的mmc‑hvdc直流短路故障穿越方法
CN108199571A (zh) * 2018-03-05 2018-06-22 南京南瑞继保电气有限公司 一种换流器保护电路和保护方法及装置
CN110970879A (zh) * 2019-12-26 2020-04-07 南京南瑞继保电气有限公司 特高压直流低端换流器阀区接地故障控制方法及控制装置

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